The Platte River watershed,the largest river basin in Nebraska(1.06×105 km^(2)),crosses the entire state along its W-E course in the approximate N-S center of Nebraska.A plethora of historical(1968-1975)hydrochem...The Platte River watershed,the largest river basin in Nebraska(1.06×105 km^(2)),crosses the entire state along its W-E course in the approximate N-S center of Nebraska.A plethora of historical(1968-1975)hydrochemistry data[major cations and anions,primarily]resulting from collection and analysis by the Nebraska Department of Environment and Energy(NDEE)were statistically and graphically analyzed and subjected to geochemical modeling.Interpretation of this large legacy dataset(31 Platte River systems sampling stations and 34 sampling sites on 22 tributaries)revealed several hydrochemical facies(Ca-HCO_(3)and three additional ones,encompassing Ca-SO_(4)and Na-SO_(4)facies solely in South Platte River discharge),and slight calcite and dolomite supersaturation comprising a line of evidence for the near thermodynamic equilibrium of the studied surface waters.Scatter plots of selected cations versus anions reveal the impact of silicate minerals(e.g.,feldspars)weathering on the aqueous hydrochemistry throughout the watershed.Relatively high concentrations of sulfate(up to 1100 mg/L)in numerous samples from the South Platte River are probably sourced by agricultural fertilizer,irrigation water,and dissolution of gypsum/anhydrite.NETPATH geochemical modeling identified 10 plausible models to simulate the significant decrease in SO_(4)levels downstream along the South Platte River.展开更多
文摘The Platte River watershed,the largest river basin in Nebraska(1.06×105 km^(2)),crosses the entire state along its W-E course in the approximate N-S center of Nebraska.A plethora of historical(1968-1975)hydrochemistry data[major cations and anions,primarily]resulting from collection and analysis by the Nebraska Department of Environment and Energy(NDEE)were statistically and graphically analyzed and subjected to geochemical modeling.Interpretation of this large legacy dataset(31 Platte River systems sampling stations and 34 sampling sites on 22 tributaries)revealed several hydrochemical facies(Ca-HCO_(3)and three additional ones,encompassing Ca-SO_(4)and Na-SO_(4)facies solely in South Platte River discharge),and slight calcite and dolomite supersaturation comprising a line of evidence for the near thermodynamic equilibrium of the studied surface waters.Scatter plots of selected cations versus anions reveal the impact of silicate minerals(e.g.,feldspars)weathering on the aqueous hydrochemistry throughout the watershed.Relatively high concentrations of sulfate(up to 1100 mg/L)in numerous samples from the South Platte River are probably sourced by agricultural fertilizer,irrigation water,and dissolution of gypsum/anhydrite.NETPATH geochemical modeling identified 10 plausible models to simulate the significant decrease in SO_(4)levels downstream along the South Platte River.
